JP5526673B2 - Solid-state imaging device and electronic device - Google Patents

Description

  The present invention relates to a solid-state imaging device including a color filter such as a digital still camera and a video camera, and an electronic apparatus using the solid-state imaging device.

  In recent years, the pixel size has been miniaturized as the number of pixels has increased. As the pixel size is reduced, the pixel area is reduced and the amount of incident light is reduced, resulting in a reduction in sensitivity. In accordance with this, the photodiode region is also narrowed, so that the number of accumulated photons is reduced, and the amount of signal at which the pixel is saturated is also reduced. Thus, a decrease in the ratio of the saturation signal amount to the sensitivity of the solid-state imaging device causes a decrease in the dynamic range.

  In general, a digital still camera or a video camera using a solid-state imaging device has a narrow dynamic range that is a range of brightness that can be captured without overexposure or blackout compared with a camera using a silver salt film. However, surveillance cameras and the like are required to be able to take an image from a dark place to a bright place, and are further required to be able to take an image without being crushed even in a dark scene.

  The dynamic range of a camera using a solid-state imaging device is usually determined by the pixel with the highest sensitivity. For example, in a camera using a solid-state imaging device equipped with green, red, and blue primary color filters, the green pixel dynamic range, which is usually the most sensitive, is the dynamic range of this camera. In the case of a solid-state imaging device that has a constant saturation signal amount for all pixels, a pixel with high sensitivity, that is, a pixel with a large amount of transmission through the color filter, first has a saturation signal amount because the number of photons accumulated in the photodiode increases. To reach.

  Conventionally, as a technique for increasing the sensitivity of a solid-state imaging device, a GRB pixel in a Bayer array in which a GRB primary color filter is disposed is replaced with a YRB array in which a Y pixel in which a filter having no absorption at a visible light wavelength is disposed. Has been proposed. In addition, a technique for improving sensitivity by replacing one of Gs arranged in a checkered pattern in a Bayer array with the above Y has been proposed (for example, see Patent Document 1).

  On the other hand, as a technique for expanding the dynamic range, a method of combining two images, a low-sensitivity image and a high-sensitivity image with different brightness, has been proposed (see, for example, Patent Document 2).

JP 2008-205940 A JP 2004-56568 A

However, the Y pixel in which the filter having no absorption at the visible light wavelength described above has a larger amount of light incident on the photodiode than the GRB pixel.
For example, as shown in FIG. 9, when the incident light quantity is taken on the horizontal axis and the pixel signal output is taken on the vertical axis, the Y pixel reaches the saturation point with an incident light quantity smaller than that of the GRB pixel. Therefore, the dynamic range D (Y) of the solid-state imaging device using Y pixels becomes narrower than the dynamic range D of the solid-state imaging device using a normal GRB filter.
Even in the solid-state imaging device using Y pixels, the dynamic range can be widened by suppressing the amount of light incident on the pixels, but the sensitivity of the solid-state imaging device is lowered.

  Also, in the technique of combining two images, a low-sensitivity image and a high-sensitivity image with different brightness, which has been proposed as a technique for expanding the dynamic range, acquisition of two images with different brightness used for composition There is a need to. As a method of obtaining two image branches having different brightness, there are a method using two cameras having different sensitivities and a method of performing exposure twice with different exposure times.

  However, when two cameras having different sensitivities are used, the two cameras are imaged side by side, so that positional deviation occurs between the two images to be captured. Further, in the method of performing exposure twice while changing the exposure time, a time difference occurs between the two images because the exposure is performed twice.

  In addition, a solid-state imaging device having pixels with different sensitivities and a solid-state imaging device in which a high sensitivity sensor and a low sensitivity sensor are embedded in one pixel have been proposed. However, in these solid-state imaging devices, it is difficult to stably produce high-sensitivity pixels and low-sensitivity pixels, and it is difficult to cope with the reduction in pixel size due to the complicated structure.

  In order to solve the above-described problems, the present invention provides a solid-state imaging device that can cope with miniaturization and can increase the dynamic range with high sensitivity.

The solid-state imaging device of the present invention includes an R pixel including an R filter that transmits red light and a B pixel including a B filter that transmits blue light. In addition, an S1 filter having a wavelength dependency of transmittance in the visible light region is provided, and an S1 pixel having higher sensitivity than the R pixel is provided. Furthermore, when the sensitivity of the pixel without the filter is 100, the sensitivity of the S1 pixel is 40 to 100, and the sensitivity of the S2 pixel is 60 or less. Then, from the output signals of the R signal, B signal, S1 signal, and S2 signal output from the R pixel, B pixel, S1 pixel, and S2 pixel, the high sensitivity neutral signal S1, the low sensitivity neutral signal S2, the Red signal R, and The Blue signal B is generated, and it is determined from the S1 signal output from the S1 pixel whether the incident light amount to the S1 pixel exceeds the light amount L1 that is the saturation point, and high sensitivity in the illuminance range until the S1 pixel is saturated. The green signal G1, the red signal R1, and the blue signal B1 are generated from the neutral signal S1, the red signal R, and the blue signal B. In the illuminance range after the S1 pixel is saturated, the low-sensitivity neutral signal S2 and the red signal Green signal G2, Red signal R2, and Blue signal B2 are generated from R and Blue signal B, and Green signal G1, R d signals R1 and Blue signals B1, and, Green signal G2, the Red signal R2 and Blue signals B2, produced by combining the single image.

  The electronic apparatus of the present invention includes a solid-state imaging device having the above-described configuration, an optical system that guides incident light to an imaging unit of the solid-state imaging device, and a signal processing circuit that processes an output signal of the solid-state imaging device.

According to the solid-state imaging device of the present invention, a filter having no wavelength dependency in transmittance in the visible light region is provided, the S1 pixel having higher sensitivity than the R pixel, and the S2 pixel having lower sensitivity than the S1 pixel are provided. . By having the S1 pixel, a highly sensitive solid-state imaging device can be obtained. Further, in one solid-state imaging device, two images of a low-sensitivity image and a high-sensitivity image having different brightness can be obtained simultaneously by the RBS1 pixel and the RBS2 pixel. An image with a wide dynamic range can be obtained by synthesizing two images of a low-sensitivity image and a high-sensitivity image with different brightness.
In addition, since the arrangement of the color filters may be changed from the conventional Bayer arrangement, it does not hinder the miniaturization of the solid-state imaging device.
According to the electronic apparatus of the present invention, it is possible to obtain an image with high sensitivity and a wide dynamic range by including the above-described solid-state imaging device.

  According to the present invention, it is possible to provide a solid-state imaging device capable of dealing with miniaturization and the like and capable of expanding the dynamic range with high sensitivity.

It is a figure which shows schematic structure of embodiment of the solid-state imaging device of this invention. It is a figure which shows embodiment of the color arrangement | sequence of the pixel part of the solid-state imaging device of this invention. It is a figure which shows the relationship between the wavelength of the incident light of the S1 filter of the solid-state imaging device of this invention, and S2 filter, the transmittance | permeability, and pixel sensitivity. It is a figure which shows the relationship between the incident light quantity and signal output for every pixel of the solid-state imaging device of this invention, and a saturation point and a dynamic range. It is a figure which shows the relationship between the incident light quantity and signal output for every pixel of the solid-state imaging device of this invention, and a saturation point and a dynamic range. It is a block diagram of the signal processing circuit of the solid-state imaging device of the present invention. It is a block diagram of the signal processing circuit of the solid-state imaging device of the present invention. It is a schematic block diagram of the electronic device which concerns on this invention. It is a figure which shows the relationship between the incident light quantity and signal output for every pixel of the pixel of the conventional solid-state imaging device, and a saturation point and a dynamic range.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following examples.
The description will be given in the following order.
1. Embodiment 2 of solid-state imaging device 2. Embodiment of pixel array and color array of solid-state imaging device Embodiment 4 of signal processing of output signal from solid-state imaging device Other embodiments of semiconductor device

<1. Embodiment of Solid-State Imaging Device>
[Configuration example of solid-state imaging device: schematic configuration diagram]
Hereinafter, specific embodiments of the solid-state imaging device of the present invention will be described.
FIG. 1 shows a schematic configuration of a MOS (Metal Oxide Semiconductor) type solid-state imaging device as an example of the solid-state imaging device of the present invention.

  A solid-state imaging device 10 shown in FIG. 1A includes a pixel unit (so-called imaging region) 13 in which pixels 12 including photodiodes serving as a plurality of photoelectric conversion units are regularly arranged in a semiconductor substrate, for example, a silicon substrate. And a peripheral circuit section. The pixel 12 includes a photodiode and a plurality of pixel transistors (so-called MOS transistors).

  The plurality of pixel transistors can be constituted by three transistors, for example, a transfer transistor, a reset transistor, and an amplification transistor. In addition, a selection transistor may be added to configure the transistor with four transistors.

  The peripheral circuit section includes a vertical drive circuit 14, a column signal processing circuit 15, a horizontal drive circuit 16, an output circuit 17, a control circuit 18, and the like.

  The control circuit 18 generates a clock signal and a control signal that serve as a reference for operations of the vertical drive circuit 14, the column signal processing circuit 15, the horizontal drive circuit 16, and the like based on the vertical synchronization signal, the horizontal synchronization signal, and the master clock. The control circuit 18 inputs these signals to the vertical drive circuit 14, the column signal processing circuit 15, the horizontal drive circuit 16, and the like.

  The vertical drive circuit 14 is configured by, for example, a shift register. The vertical drive circuit 14 sequentially selects and scans each pixel 12 of the pixel unit 13 in the vertical direction in units of rows, and a pixel based on a signal charge generated according to the amount of received light in the photoelectric conversion element of each pixel 12 through the vertical signal line 19. The signal is supplied to the column signal processing circuit 15.

  The column signal processing circuit 15 is arranged for each column of the pixels 12, for example, and outputs a signal output from the pixel 12 for one row from the black reference pixel (formed around the effective pixel region) for each pixel column. To perform signal processing such as noise removal. That is, the column signal processing circuit 15 performs signal processing such as CDS (correlated double sampling) for removing fixed pattern noise unique to the pixel 12 and signal amplification. A horizontal selection switch (not shown) is connected to the horizontal signal line 11 at the output stage of the column signal processing circuit 15.

The horizontal drive circuit 16 is configured by, for example, a shift register, and sequentially outputs horizontal scanning pulses to select each of the column signal processing circuits 15 in order, and receives a pixel signal from each of the column signal processing circuits 15 as a horizontal signal line. 11 is output.
The output circuit 17 performs signal processing and outputs the signals sequentially supplied from each of the column signal processing circuits 15 through the horizontal signal line 11.

  When the solid-state imaging device 10 is applied to a back-illuminated solid-state imaging device, a plurality of wiring layers are not formed on the back surface on the light incident surface (so-called light receiving surface) side. It is formed on the opposite surface side.

[Configuration example of color filter array and pixel array]
Next, the color arrangement of pixels in the pixel portion of the above-described solid-state imaging device will be described.
FIG. 2 is a diagram illustrating a color arrangement of pixels of the solid-state imaging device.
As shown in FIG. 2, the color arrangement of the pixel portion of the solid-state imaging device according to the present embodiment is composed of repetition of 4 pixels in 2 rows and 2 columns. These four pixels include an S1 pixel 21, an S2 pixel 22, an R pixel 23, and a B pixel 24.
The R pixel 23 includes an R filter that transmits red light. Further, the B pixel 24 has blue.
The S1 pixel 21 includes an S1 filter having a constant transmittance regardless of the transmittance of the incident light. In addition, the S2 pixel 22 includes an S2 filter having a constant transmittance regardless of the wavelength of incident light and having a transmittance lower than that of the S1 filter.
The array shown in FIG. 2 uses S1 pixels 21 and S2 pixels 22 in place of G pixels in the G, R, B (green, red, blue) color array in the Bayer array.

  The characteristics of the S1 filter and the S2 filter, which are color filters provided in the S1 pixel 21 and the S2 pixel 22, will be described with reference to FIG. In FIG. 3, the horizontal axis indicates the wavelength (nm) of light incident on the pixel, and the vertical axis indicates the transmittance of the color filters of the S1 pixel 21 and the S2 pixel. FIG. 3 shows the relationship between the wavelength of light incident on the S1 pixel 21 and the S2 pixel 22 and the pixel sensitivity for each transmittance of the S1 filter and the S2 filter. That is, the relationship between the transmittance of the S1 or S2 filter and the wavelength is shown for each incident light quantity of the pixel.

  Here, for simplification, the spectral sensitivity characteristic of the solid-state imaging device itself will be described. Since the S1 filter and the S2 filter transmit all incident wavelengths, the sensitivity of the S1 pixel 21 and the S2 pixel 22 The transmittance (%) of the S1 filter and the S2 filter can be the same. For this reason, when the transmittances of the S1 and S2 filters are 100%, the sensitivity of a pixel having a filter with this transmittance of 100% is 100%. Further, in the S1 pixel 21 and the S2 pixel 22, the sensitivity of the pixel is constant according to the transmittance of the S1 filter or the S2 filter, and the sensitivity is constant in the entire wavelength range of incident light.

When the transmittance of the S1 and S2 filters is 75%, the sensitivity of the pixel having the S1 or S2 filter with the transmittance of 75% is 75%. Similarly, when the transmittance of the S1 and S2 filters is 50%, the sensitivity of the pixel is 50%, and when the transmittance of the S1 and S2 filters is 25%, the sensitivity of the pixel is 25%.
Thus, by adjusting the transmittance of the S1 filter and the S2 filter, the sensitivity of the S1 pixel and the S2 pixel can be set to a desired value. In addition, when the spectral sensitivity characteristic of the solid-state imaging device itself is taken into consideration, the sensitivity output value can be handled in the same manner only by having wavelength dependency.

The S1 filter and the S2 filter that transmit all wavelengths in the visible light region are formed on the S1 pixel 21 and the S2 pixel 22 by vapor-depositing a metal such as aluminum, silver, or rhodium having a film thickness that provides a desired spectrum. Film. Alternatively, a material in which carbon black is dispersed in a resin at a concentration that provides a desired spectrum is formed on the S1 pixel 21 and the S2 pixel 22. The R filter and the B filter can be formed by a known method, material, or the like.
When a resin containing carbon black is used, it is possible to form the S1 and S2 filters by lithography techniques by providing photosensitivity, and the pixel having the above-described structure can be simply applied by applying the conventional technique. Can be configured.

[Explanation of relationship between amount of light incident on pixel and signal output]
Next, FIG. 4 shows signal outputs with respect to the incident light amounts of the R, B, S1, and S2 pixels. In FIG. 4, the vertical axis indicates the signal output from each pixel, the horizontal axis indicates the amount of incident light on each pixel, and the signal output from the pixel with respect to the amount of incident light on each pixel.

As described above, the color filter used in the solid-state imaging device includes four types of filters: an R filter for R pixels, a B filter for B pixels, an S1 filter for S1 pixels, and an S2 filter for S2 pixels. .
At this time, the transmittance of the S1 filter is set so that the sensitivity of the S1 pixel is higher than the sensitivity of the R pixel. Further, the transmittance of the S2 filter is set so that the sensitivity of the S2 pixel is lower than the sensitivity of the S1 pixel.

For example, the sensitivity of a pixel (G pixel) having a Green filter in a general Bayer array is indicated by a broken line G in FIG.
It is preferable to set the transmittance of the S1 filter and the S2 filter so that the S1 pixel has higher sensitivity than the G pixel and the S2 pixel has lower sensitivity than the G pixel.
In a pixel portion having a general Bayer arrangement, the sensitivity of a pixel having a Green filter is 40 to 60 when a filter having no absorption in the visible light region or a pixel sensitivity without a color filter is defined as 100. Become.
That is, in the R, B, S1, and S2 pixels described above, when the transmittance of the S1 filter is set to a filter that does not absorb in the visible light region, or the sensitivity of a pixel that does not have a color filter is set to 100, The sensitivity of the S1 pixel is set to be 40 to 100.
Further, the transmittance of the S2 filter is set so that the sensitivity of the S2 pixel is 60 or less, where 100 is a pixel where no color filter is arranged.

  Thus, by adjusting the transmittance of the S1 filter and making the sensitivity of the S1 pixel higher than that of the G pixel, the sensitivity can be made higher than that of the solid-state imaging device including the G pixel. For this reason, the output of the S1 pixel is higher than that of the normal G pixel in the range up to the incident light amount L1 at which saturation output is obtained. At this time, as shown in FIG. 4, the dynamic range D1 of the S1 pixel is narrower than the dynamic range D of the G pixel. However, as shown in FIG. 3, by using a filter having a spectrum having no absorption with respect to the wavelength of the incident light as shown in FIG. 3, all the sensitivity of the solid-state imaging device can be utilized, and the sensitivity of the solid-state imaging device is improved. Can be made.

  On the other hand, the S2 pixel can increase the amount of light reaching the saturation signal from L to L2, and can expand the dynamic range from D to D2, compared to the normal G pixel. The S2 pixel has a lower sensitivity than the G pixel, but the light amount L2 until the S2 pixel reaches the saturation point is larger than the light amount L at which the G pixel reaches the saturation point. For this reason, the dynamic range D2 of the S2 pixel can be expanded more than the dynamic range D of the G pixel.

  At this time, it is possible to further expand the dynamic range by making the sensitivity of the S2 pixel lower than that of the R pixel or the B pixel having high sensitivity. For example, as shown in FIG. 5, when the R pixel has higher sensitivity than the S2 pixel and further has higher sensitivity than the B pixel, the R, G, and S2 pixels up to the light amount L2 at which the R pixel reaches the saturation point. The dynamic range D2 can be obtained. For this reason, the configuration in which the R pixel shown in FIG. 5 has higher sensitivity than the S2 pixel and the B pixel has a higher dynamic range D2 than the configuration in which the S2 pixel shown in FIG. 4 has higher sensitivity than the R and B pixels. Can be enlarged.

As described above, when the sensitivity of the S2 pixel is lower than the higher sensitivity pixel of the R pixel or the B pixel, the incident light amount L2 and the dynamic range D2 reaching the saturation signal as shown in FIG. It depends on the pixel with the higher sensitivity of the B pixel.
The magnitude relationship between the sensitivity of the R pixel and the B pixel is arbitrarily determined depending on the spectral sensitivity characteristics other than the color filter of the mounted color filter and the color filter of the image sensor, and particularly in the configurations shown in FIGS. It is not limited.

  The sensitivity of the S2 pixel is not particularly limited as long as the sensitivity is lower than that of the S1 pixel. When the sensitivity of the S2 pixel is higher than that of the R pixel and the B pixel, the incident light amount L2 and the dynamic range D2 that reach the saturation signal as shown in FIG. 4 are determined by the sensitivity of the S2 pixel. If the sensitivity of the S2 pixel is lower than that of the R or B pixel having a high sensitivity, the incident light amount L2 and the dynamic range D2 reaching the saturation signal are determined by the sensitivity of the R or B pixel as shown in FIG. . As described above, it is not limited whether the sensitivity of the S2 pixel is higher or lower than the lower pixel of the R pixel or the B pixel.

  Therefore, in the solid-state imaging device having the pixel portion of the R, B, S1, and S2 pixel arrangement having the above-described configuration, the sensitivity is increased by the S1 pixel, the R pixel, and the B pixel in the incident light amount up to L1 where the S1 pixel reaches the saturation point. High-quality images can be synthesized. In addition, an image having a wide dynamic range can be synthesized by the S2 pixel, the R pixel, and the B pixel at an incident light amount equal to or more than L1 at which the S1 pixel reaches the saturation point.

[Example of Signal Processing for Generating Image from Output Signal: Configuration Example 1]
Next, a first example of a signal processing circuit for generating the luminance signal Y and the color difference signal C from the pixel output used for the above signal processing will be described. FIG. 6 shows a block diagram of the signal processing circuit 30 of the first example.

  First, the pixel interpolation calculation unit 31 receives the R signal, B signal, S1 signal, and S2 signal output from the R pixel, B pixel, S1 pixel, and S2 pixel of the solid-state imaging device. Then, a high-sensitivity neutral signal S1, a low-sensitivity neutral signal S2, a Red signal R, and a Blue signal B are generated for each pixel from the output signal by a known pixel interpolation process.

In the pixels of the above-described R, B, S1, and S2 arrangement, the filters of the S1 pixel and the S2 pixel are neutral (the transmittance is not biased in the visible light wavelength region), and therefore the same by multiplying each other by a coefficient. It can be handled in the same way as a signal from a spectral pixel.
That is, the transmittances of the S1 filter and the S2 filter have a constant transmittance without absorption of visible light, as shown in the graph of FIG. Here, the ratio between the sensitivity of the S1 pixel and the sensitivity of the pixel equipped with a filter that does not absorb visible light at all is a1. Further, the ratio between the sensitivity of the S2 pixel and the sensitivity of the pixel equipped with a filter that does not absorb visible light at all is a2. At this time, a signal that can be handled in the same manner as the low-sensitivity neutral signal S2 can be generated from the high-sensitivity neutral signal S1 by the following equation (1). Further, from the following equation (2), a signal that can be handled in the same manner as the high-sensitivity neutral signal S1 can be generated from the low-sensitivity neutral signal S2.
S1 = (S2 / a2) × a1 (1)
S2 = (S1 / a1) × a2 (2)

  Therefore, for example, as shown in FIG. 2, the S1 pixel and the S2 pixel are alternately arranged at the position of the G pixel in the Bayer array. With this configuration, while having four types of pixels having different spectral characteristics, it is possible to obtain the same resolution as when a Bayer array solid-state imaging device is used in the range of incident light amounts up to L1.

  Further, since the S1 pixel is saturated in the range exceeding the incident light amount L1, it is necessary to generate the low sensitivity neutral signal S2 at the S1 pixel position. The low-sensitivity neutral signal S2 at the S1 pixel position is generated by interpolation processing using the signal of the S2 pixel using the above equation (2).

Further, the S1 pixel saturation determination unit 35 determines whether the incident light amount exceeds L1.
In addition to the pixel interpolation calculation unit 31 described above, an output signal from the S1 pixel is sent to the S1 pixel saturation determination unit 35. Then, the S1 pixel saturation determination unit 35 determines from the output signal sent from the S1 pixel whether the incident light amount to the S1 pixel exceeds the light amount L1, which is the saturation point, and determines whether the S1 pixel is saturated. .

  If the amount of incident light does not exceed L1, the pixel interpolation calculation unit 31 is instructed to generate the high sensitivity neutral signal S1 using the S1 signal at the S2 pixel position. Further, when the incident light quantity exceeds L1, the pixel interpolation calculation unit 31 is instructed to generate the low sensitivity neutral signal S2 using the S2 signal at the S1 pixel position.

  Next, the G calculation unit 32 generates a green signal G1, a red signal R1, and a blue signal B1 from the high sensitivity neutral signal S1, the red signal R, and the blue signal B. Further, a green signal G2, a red signal R2, and a blue signal B2 are generated from the low sensitivity neutral signal S2, the red signal R, and the blue signal B.

Here, as described above, the ratio between the sensitivity of the S1 pixel and the S2 pixel and the sensitivity of the pixel on which a filter having no visible light absorption is mounted is a1 and a2, respectively.
At this time, the Green signal G1, the Red signal R1, and the Blue signal B1, which are signals for generating a high-sensitivity image, are expressed by the following equation (3) using the high-sensitivity neutral signal S1, the Red signal R, and the Blue signal B. Can be obtained. Then, the green signal G2, the red signal R2, and the blue signal B2, which are signals for generating a low-sensitivity image, are obtained by the following equation (4) using the low-sensitivity neutral signal S2, the red signal R, and the blue signal B. Can do.
G1 = S1-a1 (R + B), R1 = R, B1 = B (3)
G2 = S2-a2 (R + B), R2 = R, B2 = B (4)

Further, the green signal G1, the red signal R1, and the blue signal B1, which are signals for generating a high-sensitivity image, are obtained by the following equation (5) using the high-sensitivity neutral signal S1, the red signal R, and the blue signal B. You can also Then, the green signal G2, the red signal R2, and the blue signal B2, which are signals for generating a low-sensitivity image, are obtained by the following equation (6) using the low-sensitivity neutral signal S2, the red signal R, and the blue signal B. You can also.
G1 = (S1 / a1) − (R + B), R1 = R, B1 = B (5)
G2 = (S2 / a2)-(R + B), R2 = R, B2 = B (6)

  A green signal G1, a red signal R1, and a blue signal B1 for generating a high-sensitivity image using the equations (3) to (6) in the G calculation unit 32, and a green signal G2, for generating a low-sensitivity image, A Red signal R2 and a Blue signal B2 are generated.

  Subsequently, the first MTX calculation unit 33 performs matrix calculation processing such as white balance, linear matrix processing, and color difference matrix processing on G1, R1, and B1 to generate a high sensitivity image luminance signal Y1 and a high sensitivity image color difference signal C1. . The high-sensitivity image luminance signal Y1 and the color difference signal C1 are high-sensitivity images corresponding to the high illuminance side up to the incident light amount L1 (FIG. 4) where the S1 pixel is saturated.

  Similarly, the second MTX calculation unit 34 performs matrix calculation processing such as white balance, linear matrix processing, and color difference matrix processing on G2, R2, and B2 to generate a low sensitivity image luminance signal Y2 and a low sensitivity image color difference signal C2. The low-sensitivity image luminance signal Y2 and the color difference signal C2 are low-sensitivity images corresponding to the incident light amount exceeding the incident light amount L1 (FIG. 4) at which the S1 pixel is saturated.

Then, the high-sensitivity image based on the high-sensitivity image luminance signal Y1 and the high-sensitivity image color difference signal C1 and the low-sensitivity image based on the low-sensitivity image luminance signal Y2 and the low-sensitivity image color difference signal C2 are processed in the image composition unit 36. Synthesize. At this time, if the saturation of the S1 pixel is not detected by the S1 pixel saturation determination unit 35, an image is generated only from the high-sensitivity image.
When the saturation of the S1 pixel is detected, the luminance signal Y1 and the color difference signal C1 of the high-sensitivity image are used for the pixels with the incident light quantity up to L1 from these two images. And in the pixel whose incident light quantity exceeded L1, the luminance signal Y2 and color difference signal C2 of a low sensitivity image are used. In this way, one image is generated by synthesis by using the high-sensitivity image signal and the low-sensitivity image signal in the pixels up to the incident light amount L1 and the pixels exceeding the incident light amount L1, respectively.
At this time, if the pixel signal used in the incident light amount L1 is switched, the synthesized image becomes unnatural. For this reason, it is possible to generate a natural image by various known methods such as changing the synthesis ratio of the signals of the respective images depending on the amount of incident light.

[Example of Signal Processing for Generating Image from Output Signal: Configuration Example 2]
Next, a second example of the signal processing circuit for generating the luminance signal Y and the color difference signal from the pixel output using the above-described signal processing will be described. FIG. 7 shows a block diagram of the signal processing circuit 40 of the second example. In the following description, the same configuration as that of the signal processing circuit 30 of the first example shown in FIG.

  First, similarly to the first example of the signal processing circuit described above, in the pixel interpolation calculation unit 41, the R signal, the B signal, and the S1 signal output from the R pixel, the B pixel, the S1 pixel, and the S2 pixel of the solid-state imaging device. And S2 signal. Then, a high-sensitivity neutral signal S1, a low-sensitivity neutral signal S2, a Red signal R, and a Blue signal B are generated for each pixel from the output signal by a known pixel interpolation process. The generation of the high-sensitivity neutral signal S1, the low-sensitivity neutral signal S2, the Red signal R, and the Blue signal B in the pixel interpolation calculation unit 41 of the signal processing circuit of the second example is performed by the signal processing circuit of the first example described above. This can be performed in the same manner as the pixel interpolation calculation unit. Similarly to the signal processing circuit of the first example, the S1 pixel saturation determination unit 42 determines whether the incident light amount exceeds L1. And in the range exceeding the incident light quantity L1, the low sensitivity neutral signal S2 is produced | generated by the interpolation process using the signal of S2 pixel in S1 pixel position.

Next, the S calculation unit 43 combines the high sensitivity neutral signal S1 generated by the pixel interpolation calculation unit 41 and the low sensitivity neutral signal S2 to generate the neutral signal S.
At this time, the S1 pixel saturation determination unit 42 determines which of the high sensitivity neutral signal S1 and the low sensitivity neutral signal S2 is used in each pixel.
The high sensitivity neutral signal S1 is used in the range up to the incident light amount L1, that is, the pixel having the incident light amount in the range where the S1 pixel is not saturated. The low-sensitivity neutral signal S2 is used for pixels having an incident light amount exceeding the incident light amount L1, that is, in a range where the S1 pixel image is saturated. At this time, in the vicinity of the incident light quantity L1, it is possible to generate a more natural image by changing the composition ratio of the high sensitivity neutral signal S1 and the low sensitivity neutral signal S2 with respect to the incident light quantity.

Next, in the G calculation unit 44, the green signal G3, the red signal R3, and the blue signal B3 from the neutral signal S generated by the S calculation unit 43 and the red signal R and the blue signal B generated by the pixel interpolation calculation unit 41. Is generated.
At this time, if the ratio between the sensitivity of the S1 pixel and the sensitivity of the pixel equipped with a filter that does not absorb visible light at all is a1, the Green signal G3, the Red signal R3, and the Blue signal B3 can be expressed by Equation (7) or It is obtained by (8).
G3 = S−a1 (R + B), R3 = R, B3 = B (7)
G3 = S3 / a1- (R + B), R3 = R, B3 = B (8)

  Subsequently, in the MTX calculation unit 45, the green signal G3, the Red signal R3, and the Blue signal B3 generated by the G calculation unit 44 are subjected to matrix calculation processing such as white balance, linear matrix processing, color difference matrix processing, etc. A color difference signal C is generated.

When the amount of incident light is small, a highly sensitive image can be obtained by the S1 pixel. Furthermore, the dynamic range can be expanded to the incident light amount L2 that becomes the saturation point of the S2 pixel by using the low-sensitivity S2 pixel. Thus, even with the incident light quantity at which the S1 pixel is saturated, the S2 pixel provided with the S2 filter whose sensitivity is lower than that of the S1 pixel is not saturated. By synthesizing the output signals of the S1 pixel and S2 pixel by the above-described method, the luminance signal Y and the color difference signal C can be obtained to synthesize one image.
Since both the S1 pixel filter and the S2 pixel filter transmit all wavelengths, by applying the coefficients a1 and a2, it is possible to treat the same signal as the signal from the same spectral pixel.
Therefore, if the arrangement of the S1 pixel and the S2 pixel is alternately arranged at the position of the G pixel in the Bayer arrangement, for example, as shown in FIG. 2, the Bayer arrangement solid-state imaging device having four types of pixels having different spectral characteristics. It is possible to obtain the same resolution as when using.
In addition, by providing the S1 pixel and the S2 pixel, it is possible to obtain a high-sensitivity image and a low-sensitivity image without reducing the resolution of a solid-state imaging device having a conventional Bayer array. Then, it is possible to provide a solid-state imaging device and a camera system that achieve both high sensitivity and a wide dynamic range.

<3. Example of electronic device configuration>
The solid-state imaging device according to the present invention can be applied to electronic devices such as a camera equipped with a solid-state imaging device, a portable device with a camera, and other devices equipped with a solid-state imaging device.
FIG. 8 shows a schematic configuration when a solid-state imaging device is applied to a digital still camera capable of taking a still image as an example of the electronic apparatus of the present invention.

  The camera 50 according to the present embodiment includes an optical system (optical lens) 51, a solid-state imaging device 52, a signal processing circuit 53, and a drive circuit 54.

  As the solid-state imaging device 52, the above-described solid-state imaging device is applied. The optical lens 51 forms image light (incident light) from the subject on the imaging surface of the solid-state imaging device 52. As a result, signal charges are accumulated in the photoelectric conversion element of the solid-state imaging device 52 for a certain period. The drive circuit 54 supplies a transfer operation signal for the solid-state imaging device 52. Signal transfer of the solid-state imaging device 52 is performed by a drive signal (timing signal) supplied from the drive circuit 54. The signal processing circuit 53 performs various signal processing on the output signal of the solid-state imaging device 52. As the signal processing circuit 53, the signal processing circuit 30 shown in FIG. 6 or the signal processing circuit 40 shown in FIG. 7 can be used. The video signal subjected to the signal processing is stored in a storage medium such as a memory or output to a monitor or the like. The camera 50 according to the present embodiment includes a camera module in which an optical lens 51, a solid-state imaging device 52, a signal processing circuit 53, and a drive circuit 54 are modularized.

The present invention can constitute a camera-equipped portable device such as a mobile phone provided with the camera of FIG. 8 or a camera module.
Furthermore, the configuration of FIG. 8 can be configured as a module having an imaging function in which the optical lens 51, the solid-state imaging device 52, the signal processing circuit 53, and the drive circuit 54 are modularized, a so-called imaging function module. The present invention can constitute an electronic apparatus provided with such an imaging function module.

  In the above-described embodiment, a CMOS image sensor has been described as an example of a solid-state imaging device. However, the present invention can also be applied to a solid-state imaging device other than a CMOS image sensor. The present invention can be realized by changing the color filter arrangement of a general-purpose solid-state imaging device. The type of the solid-state imaging device is a CCD (Charge Coupled Device) image sensor, a CMD (Charge Modulation Device) image sensor, or the like. Regardless of type and method. In addition, the application range of the system according to the present invention can be applied to a figure due to limitations imposed by the camera system such as still images and moving images.

  The present invention is not limited to the configuration described in the above-described embodiment, and various modifications and changes can be made without departing from the configuration of the present invention.

  DESCRIPTION OF SYMBOLS 10 Solid-state imaging device, 11 Horizontal signal line, 12 pixels, 13 pixel part, 14 Vertical drive circuit, 15 Column signal processing circuit, 16 Horizontal drive circuit, 17 Output circuit, 18 Control circuit, 19 Vertical signal line, 21 S1 pixel, 22 S2 pixel, 23 R pixel, 24 B pixel, 30, 40 signal processing circuit, 31, 41 pixel interpolation calculation unit, 32, 44 G calculation unit, 33 first MTX calculation unit, 34 second MTX calculation unit, 35, 42 S Pixel saturation determination unit, 36 image composition unit, 43 S calculation unit, 45 MTX calculation unit, 50 camera, 51 optical system, 52 solid-state imaging device, 53 signal processing circuit, 54 drive circuit

Claims (3)

An R pixel including an R filter that transmits red light;
A B pixel including a B filter that transmits blue light;
An S1 filter having a wavelength dependency of transmittance in the visible light region, and having a higher sensitivity than the R pixel;
Whereby the wavelength dependence of transmittance in the visible light region, comprising a step S1 a low transmittance S2 filter of visible light than the filter, Bei give a, S2 with a pixel of lower sensitivity than step S1 pixel,
When the sensitivity of a pixel without a filter is 100, the sensitivity of the S1 pixel is 40 to 100, and the sensitivity of the S2 pixel is 60 or less,
From the R signal, the B signal, the S1 signal, and the S2 signal output signals output from the R pixel, the B pixel, the S1 pixel, and the S two pixel, a high sensitivity neutral signal S1, a low sensitivity neutral signal S2, and a Red signal. R and Blue signal B are generated,
From the S1 signal output from the S1 pixel, determine whether the incident light amount to the S1 pixel exceeds a light amount L1 that is a saturation point,
In the illuminance range until the S1 pixel is saturated, the green signal G1, the red signal R1, and the blue signal B1 are generated from the high sensitivity neutral signal S1, the red signal R, and the blue signal B.
In the illuminance range after the S1 pixel is saturated, the Green signal G2, the Red signal R2, and the Blue signal B2 are generated from the low sensitivity neutral signal S2, the Red signal R, and the Blue signal B.
A solid-state imaging device comprising: generating one image from the green signal G1, the red signal R1, and the blue signal B1, and the green signal G2, the red signal R2, and the blue signal B2 by synthesis .   The solid-state imaging device according to claim 1, wherein the S2 pixel has lower sensitivity than a pixel having higher sensitivity of the R pixel or the B pixel. A solid-state image sensor,
An optical system for guiding incident light to the imaging unit of the solid-state imaging device;
A signal processing circuit for processing an output signal of the solid-state imaging device ,
The solid-state imaging device is
An R pixel including an R filter that transmits red light;
A B pixel including a B filter that transmits blue light;
An S1 filter having a wavelength dependency of transmittance in the visible light region, and having a higher sensitivity than the R pixel;
An S2 filter having no wavelength dependency of transmittance in the visible light region and having a visible light transmittance lower than that of the S1 filter, and an S2 pixel having a sensitivity lower than that of the S1 pixel;
When the sensitivity of a pixel without a filter is 100, the sensitivity of the S1 pixel is 40 to 100, and the sensitivity of the S2 pixel is 60 or less,
From the R signal, the B signal, the S1 signal, and the S2 signal output signals output from the R pixel, the B pixel, the S1 pixel, and the S two pixel, a high sensitivity neutral signal S1, a low sensitivity neutral signal S2, and a Red signal. R and Blue signal B are generated,
From the S1 signal output from the S1 pixel, determine whether the incident light amount to the S1 pixel exceeds a light amount L1 that is a saturation point,
In the illuminance range until the S1 pixel is saturated, the green signal G1, the red signal R1, and the blue signal B1 are generated from the high sensitivity neutral signal S1, the red signal R, and the blue signal B.
In the illuminance range after the S1 pixel is saturated, the Green signal G2, the Red signal R2, and the Blue signal B2 are generated from the low sensitivity neutral signal S2, the Red signal R, and the Blue signal B.
An electronic device that generates one image from the green signal G1, the red signal R1, and the blue signal B1, and the green signal G2, the red signal R2, and the blue signal B2 by synthesis .

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